What is the belly button

A pierced belly button.

Mammals are split into three groups: placentals, monotremes, and marsupials. Placental mammals are by far the greater and most diverse group of the three, carrying this name because they nourish their offspring through a placenta (the name is somewhat of a misnomer since marsupials also have a placenta).

The placenta is essentially an organ that connects the developing fetus to the uterine. As the fetus is carried in the uterus of its mother to a relatively late stage of development, it gets all of its necessary nutrients through the placenta. The placenta also provides oxygen and removes waste products from the fetus’ blood.

The placenta attaches itself to the wall of the uterus, and the fetus’s umbilical cord develops from the placenta. After birth, when the placenta is separated from the baby, the resulting scar tissue (a hollowed or sometimes raised area) is clinically called the umbilicus. Colloquially, it’s called the navel or the belly button.

So there you have it — your belly button is probably your first scar.

Humans aren’t the only ones to have belly buttons — most mammals do. However, it’s often hidden beneath fur and is much less visible.

Innie vs Outie

Among the most common misconceptions about the belly button is the innie (or inny) versus outie debate. Contrary to popular belief, this isn’t decided by where the umbilical cord is cut, but rather by how the scar tissue forms and then dries (remember, the belly button is basically scar tissue). As far as anyone can tell, this process is random, but the innie is much more common than the outie.

An “innie”. Credits: Stinkie Pinkie / Wikipedia.

Umbilical hernias (when the baby’s abdominal wall layers don’t join completely) can cause the belly button to push outward, even though they are often painless and don’t cause any discomfort.

Sometimes, the inner pressure can turn a pregnant woman’s navel from an innie to an outie. Extreme weight gain can do the same thing.

Is the belly button useful?

Da Vinci’s Vitruvian man has the navel at its center.

The belly button doesn’t have any biological uses, though it is used in some medical procedures. For instance, if a transfusion is necessary for a newborn, the umbilical cord stump is preferred.

Visually, the umbilicus is used to visually separate the abdomen into quadrants and is often regarded as the body’s center of balance, serving as an important anatomical landmark. It’s also used for introducing laparoscopic ports during laparoscopic surgery and can be a tell-tale sign of intra-abdominal pathologies.

Abdominal regions are used for example to localize pain, and the navel serves as an anatomic landmark.

An abnormal belly button shape can also be an indicator of pregnancy problems.

Lastly, it can also serve an aesthetic role — although many people would regard the navel as aesthetically unpleasant, others pierce and tattoo it, and there’s even a navel fetish: in 2012, it was the second most popular fetish search on Google.

Belly button facts

You never knew you wanted to learn about the belly button, didn’t you? Well, in 2012, a biological study found that the “fauna” in your navel is much like that of a tropical forest — the bacterial fauna, that is. According to researchers, thousands and thousands of bacteria types (some new to science) can be found in your belly button, but there’s no reason to worry: they’re quite harmless.

If you thought that’s disturbing, wait ’til you hear this: you can actually make cheese using the bacteria in the navel. As part of a collaborative project named “Selfmade”, biologist Christina Agapakis and odor artist Sissel Tolaas made 11 new types of cheese from the bacteria found in armpits, mouths, toes, and belly buttons.

In an article published in 2000 in the journal Plastic and Reconstructive Surgery, scientists tried to discuss what the perfect belly button looks like. The article, entitled In search of the ideal female umbilicus, had participants rate different types of belly buttons. They found that the T- or vertically shaped umbilicus with superior hooding consistently scored the highest in aesthetic appeal, and the “outie” was almost universally displeasing. Considering that several thousand people are having navel plastic surgery each year (and the trend is increasing), that can be quite useful to know. Interestingly, breast implant surgeries can also be done through the navel in order to avoid scarring; it’s called Trans-umbilical breast augmentation.